Skip Links

Fact Sheet 2006–3095

About USGS /  Science Topics /  Maps, Products & Publications /  Education / Publication: FAQ

1976 Big Thompson Flood, Colorado—Thirty Years Later

By Robert D. Jarrett and John E. Costa

thumbnail of frontpageDownload Publication
Fact Sheet 2006-3095
PDF (6.4 MB)
Right-Click to 'Save As' or 'Download'

In the early evening of Saturday, July 31, 1976, a large stationary thunderstorm released as much as 7.5 inches of rainfall in about an hour (about 12 inches in a few hours) in the middle reaches of the Big Thompson River Basin and to a lesser extent in parts of the Cache la Poudre River Basin. In steep mountain terrain with thin or no soil, this large amount of rainfall in such a short period of time produced a flash flood that caught residents and tourists by surprise. The sudden flood that churned down the narrow Big Thompson Canyon scoured the river channel that night, caused over $35 million in damages (1977 dollars) to 418 homes and businesses, many mobile homes, 438 automobiles, numerous bridges, paved and unpaved roads, power and telephone lines, and many other structures. The tragedy claimed the lives of 144 people, including two law enforcement officers trying to evacuate people in danger, and there were 250 reported injuries. Scores of other people narrowly escaped with their lives. More than 800 people were evacuated by helicopter the following morning. This fact sheet presents a summary of the hydrologic conditions of the 1976 flood, describes some of the advances in U.S. Geological Survey (USGS) flood science as a consequence of this disaster, and provides a reminder that extreme floods like the 1976 Big Thompson flood have occurred in other locations in Colorado in the past and will occur again.

Version 1.0

Posted July 2006

  • Fact Sheet PDF (6.4 MB)
    (This report is accessible as defined in Section 508 of the Rehabilitation Act of 1973, Amendments of 1998.)

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Acrobat Reader or similar software is required to view it. Download the latest version of Acrobat Reader, free of charge or go to for free tools that allow visually impaired users to read PDF files. logo  Take Pride in America button